Check data corresponding to distributed confidential information is generated, and the confidential information and check data are distribution-coded. When the confidential information is restored, the confidential information and check data are restored and it is determined whether or not the restored check data correspond to the restored confidential information. If the data correspond to the information, the information is determined to be correct and is output. If not, the information is judged to be false (i.e., tampered distributed information), and a symbol indicating that falsity has been detected is output.